Reports that heavily armed SAS soldiers were deployed during the London Bridge terror attack, and the NSW coroner's recent findings on the Lindt cafe siege, have put Australia's military "call out" powers firmly back in the spotlight.

Federal cabinet will soon consider the findings of a review examining whether legislative changes are needed to allow Australia's Defence Force assets to be called out more quickly, decisively and legally following terrorist incidents.

Specifically it's looking at Part III AAA of the Defence Act 1903, which deals with the "Utilisation of Defence Force to protect Commonwealth Interests and States and Self-governing Territories".

The review of Defence's support to national counterterrorism arrangements has been underway since last year, but senior figures in the department and the military privately insist no legislative change is necessary.

Soldiers would look to 'use lethal force immediately'

"Our current laws allow specialised counterterror personnel to be deployed very quickly," one senior Army figure told the ABC.

"During the Lindt siege our special forces soldiers were ready to go if they were called upon by the government," the officer said.

"What the public needs to understand though is that once the military is 'called out' things have gotten really bad — special forces will be aiming to use lethal force immediately, whereas in the first instance police are not generally looking to use their weapons."

Another senior defence official said while TAG East (the Tactical Assault Group at Holsworthy Barracks) had constructed a mock-up of the Lindt cafe and was ready to deploy, last month's NSW coroner's report made it very clear military "call out" powers did not need to be used in the 2014 hostage siege.

The Australian Strategic Policy Institute's Jacinta Carroll believes what's needed is a "high level of understanding of how the current legislation works".

"There just isn't that understanding and practice about what's different between state and federal police powers and the role of the military in a call out," Ms Carroll argues.

"In talking about call out those who are discussing it need to be clear what will happen and what they think those roles will be."

Calls for more decision-making exercises

A long-serving and former Australian special forces soldier, who can't be identified, said what's needed is more "decision-making" exercises to ensure all governments are well rehearsed and prepared for a mass casualty or hostage-taking incident.

Calling on the army to aid a security operation is incredibly rare in Australia, and by general consensus, the last time was in 1978 as part of the Commonwealth Heads of Government Regional Meeting, which was rocked by the Hilton Hotel Bombing.

The reasons for the sparing use of military power are mostly legal, but are built on a moral principle too.

Australia's military was created to protect the country against "invasion" and no man or woman has ever enlisted to use lethal force against fellow Australians.

However national security policy makers and many others in government are increasingly anxious that a combination of rapidly changing terrorist tactics, modern weaponry, vast geography and the varying strengths of state police forces may necessitate a rethink.

During a recent Senate estimates hearing Defence Minister Marise Payne was questioned about the review of call out powers which will soon be considered by Cabinet.